1. Field of the Invention
The present invention relates in general to well production devices and, in particular, to a self-controlled inflow control device.
2. Brief Description of Related Art
Some well completions use lateral lines to penetrate horizontally across a reservoir. These horizontal well sections extend through a reservoir at the same general elevation to produce fluid from across the reservoir rather than a localized area around a vertical well. The lateral lines extend from a heel at the junction of the lateral line with the vertical line to a toe at the end of the lateral line. Fluid along the horizontal wellbore profile will flow into the production tubing all along the lateral. However, the fluid flowing into the heel will block flow from the toe, preventing production of fluid from the entire reservoir profile to the surface. Instead, the majority of the produced fluid will be drawn from the formation areas around the heel. This may lead to coning. Coning refers to the cone shape reservoir fluid movement front, i.e. a boundary between desired reservoir fluid and undesired reservoir fluid, when too much reservoir production occurs from a single zone of the well. As reservoir fluid is produced from the formation, surrounding fluids, such as water, will flow into the produced areas. If the produced fluid flowrate is too high, the water will fill the area before desired fluid can replace the produced fluid. In a lateral well, production only at the heel will draw water into the formation at the heel. As the heel produces water, it will block formation fluid from the toe. In these situations, inflow control devices (ICDs) are used to restrict the flow of reservoir fluid from the heel and other high pressure areas of the formation to create a more even production profile that produces reservoir fluid from the formation and prevent coning.
Inflow control devices restrict flow by forcing fluid through restricted passageways to create a pressure differential. This pressure differential must be overcome by the pressure in the reservoir surrounding the inflow control device. Where reservoir pressure is high, the pressure will overcome the inflow control device pressure differential and be produced to the surface. As production causes a pressure drop in the reservoir around the inflow control device, the reservoir pressure will no longer overcome the inflow control device pressure differential, limiting production from that area until reservoir pressure increases. Reservoir formations are tested before the inflow control devices are run-in-hole, and the inflow control devices are adjusted prior to run-in to accommodate the pressure for the specific zone of the reservoir in which the inflow control device is placed. These inflow control devices have difficulties maintaining the desired production profile for longer production periods, eventually completely stopping production as the reservoir pressure drops. To overcome this, some inflow control devices include mechanisms that allow the inflow control device to vary the pressure differential to accommodate reservoir pressure changes. These inflow control devices use hydraulically controlled functions powered by hydraulic umbilicals that supply fluid pressure from the surface. These inflow control devices are significantly more expensive to use due to the specialty equipment needed to run the hydraulic umbilical and monitor it from the surface.
In addition, many inflow control devices are unable to actively restrict the fluid flowrate of reservoir fluid through the inflow control device and adjust for reservoir fluid flow that has a high volume of gas or a high volume of water in the flow. Thus, if a portion of the well begins to produce a gas or water, the inflow control device cannot further restrict flow to limit the percentage of water or gas in the fluid produced at the surface. Some inflow control devices include equipment that may be operated from the surface to accommodate for these situations, but similar to the hydraulic pressure adjustment equipment, the inflow control devices need expensive hydraulic or electric umbilicals to perform the water and gas restriction function. These inflow control devices also require an extensive and expensive testing process to determine which portion of the well is producing the water and gas. Still further, some inflow control devices include means to restrict water and gas flow using devices that respond to varying fluid density in the reservoir. These devices must then mate with corresponding nozzles to restrict fluid flow. However, many of these devices are unable to successfully operate outside of specific known density conditions. Thus, in the event there is a significant variance in the expected reservoir fluid density, the devices are unable to properly limit flow of the water or gas. Typically, these devices may only accommodate restriction of either water or gas, but not both.
Another problem faced by use of inflow control devices, particularly in well formations using an openhole production process is clogging of filter media. As the inflow control device is used, particulate matter builds up on the filter and blocks flow of fluid from the reservoir into the inflow control device and production tubing. Still another problem faced by inflow control devices is the inability of the inflow control device to be choked back or turned off by an operator at the surface to prevent flow of reservoir fluid through the inflow control device under predetermined conditions. Therefore, an inflow control device that overcomes the problems of the prior art described above would be desirable.